Sampling and counting soil fauna

Transcription

1 Sampling and counting soil fauna Follow-up notes from workshop on soil biology held with University of Western Australia and Bugs & Biology Grower Group Friday 20 th July 2012 The information presented in these notes was prepared by the SPICE program for the Monitoring Soil Science project. SPICE is a secondary science teachers enrichment program and is a partnership between the WA Department of Education and The University of Western Australia. For more information: We are grateful to SPICE for permission to reproduce these materials.

2 These notes give an overview of the methods used to extract and count soil fauna, as demonstrated by staff and students from the University of Western Australia during the workshop co-ordinated by Bugs & Biology Grower Group on Friday 20 July. The notes include the following components: 1) Equipment 2) Safety aspects 3) Collecting soil samples 4) Extracting soil fauna 5) Identifying and counting soil fauna 6) Further information 7) Background sheet on mites and springtails We are grateful to the SPICE program for permission to reproduce extracts from their manual on Monitoring Soil Science ( 1. Equipment To sample the soils you will need: Sampling ring (e.g. cut of section of PVC pipe. Cut to 6 cm lengths and mark a few dots or crosses at 1 cm depth inside the ring with permanent marker) Trowel Flat surface large enough to cover surface of sampling ring (e.g. paint scraper) Plastic zip-loc bags Gloves To extract soil fauna you will need: Soil samples Funnel and container (made from 1.5 L soft drink bottle) Lamp (source of heat and light) Gauze swabs (2 per sampling apparatus) Mesh (square of flywire) Collecting containers with lids of approx 70 ml (e.g. specimen containers), preferably with 1 cm layer of plaster of paris and charcoal at the bottom (see instructions) To identify soil fauna you will need Classification sheets (to note down results) Basic identification charts (e.g. Microscope Container with collected soil samples Petri dish or other clear, flat dish 70% alcohol to preserve specimens Specimen tube if you wish to keep specimens 1

3 2. Safety aspects 3. Collecting soil samples We recommend soil samples are taken first thing in the morning. The ground is cooler then, and soil fauna are likely to be nearer the surface. Soil fauna abundance will vary throughout the year. Soil fauna biomass tends to be greatest in the top few centimetres of soil when the soil is moist. In dry summer months soil fauna abundance made be lower, or you may find that the species that are present are very different to those present in winter. When sampling soils, record the date, time, ambient temperature (approx) and weather conditions (sunny, raining, overcast). Push the sampling ring 5 cm into the ground. Where a litter layer is present, you should also collect whatever litter is found in the top 1 cm of the sampling ring (which should be above the level of the soil). If the litter layer is greater than 1 cm, brush off the top so that only the lower 1 cm is collected. See below for step-by-step instructions on sampling soil. 2

4 If you wish to keep your soil fauna alive, follow the instructions below to prepare a layer of permeable material at the bottom of the collecting jars prior to taking soil samples. Periodically add a couple of drops of water to the containers to keep the organisms alive and moist during the extraction. 4. Extracting soil fauna A simple device for extracting soil fauna can be made by cutting the top of a 1.5 L soft drink container, and using this as a funnel to collect soil fauna in the bottom of the soft drink bottle. The instructions below detail how to make this simple device; these are the same instructions that were used to create the sampling devices on display during the field day. Instructions: You can put sand or gravel in the bottom of the 1.5 litre soft drink container to stop the bottle from accidentally tipping over. You should leave all your soil samples for around the same time (e.g. all 48 hours regardless of when collected) 3

5 5. Identifying and counting soil fauna Look at the soil fauna under a microscope. Use the mite and springtail identification sheets to count the number of mites and number of springtails in each sample. Record your results on your record sheet. If the mites and springtails are too mobile to count, tip them into a Petri dish containing a thin film of 70% alcohol (if there is too much liquid, the animals will move around as you move the dish, making it difficult to keep track of how many animals there are. You may like to keep your specimens afterwards by preserving in 70% alcohol and labelling. You can compare soil fauna abundance and diversity from different parts of your property, or you might like to compare soil from one part of your property at different points in time. Soil fauna are known to be highly variable in space and time, so it is advisable to take multiple samples (perhaps 3 to 5) from a particular area of interest to avoid an atypical result. It is difficult to specify an ideal soil fauna result or community for any particular area, given that soil fauna are so diverse and occupy many ecological niches. Generally speaking, a healthy soil fauna community is diverse (i.e., many different types of soil fauna are present, without overdomination by one species) and abundant (i.e., relatively high number of individuals). 6. Further information Fact sheets with identification pictures are available on springtails, mites and soil fauna: (available as.pdf files) Podcasts demonstrating the methods outlined in this note: Sampling soil: Extracting soil fauna: Further information on the Monitoring Soil Science project with schools is available at: For further detailed information on soil biology, see Soils are Alive on: For further information contact: Professor Lynette Abbott School of Earth and Environment University of Western Australia lynette.abbott@uwa.edu.au or Natasha Pauli Assistant Professor School of Earth and Environment (M004) University of Western Australia 35 Stirling Highway Crawley 6009 natasha.pauli@uwa.edu.au Phone:

6 Background information on mites and springtails 7. Background sheet on mites and springtails 5

7 6 Background information on mites and springtails